This reminds me a lot of a minigame in New Super Mario Bros DS (maybe also in 64 DS)! The art is really nice - I especially like the separate sprites for picked-up robots.
I think the magnet is a lot better than the tweezers. Even if you just want to pick up a single robot out of a crowd, you can just grab the robot using the edge of the magnet hitbox. The magnet is more fun to use, anyways!
I did find a crash, however - if you try to pick up a robot whilst it's still spawning, you get a RuntimeError. This gets pretty unavoidable as things pick up!
Great job on the game!!